Such devices for the dosed administration of sprayable substances can especially be configured as inhalers and can be employed in medicine for the treatment of diseases. Such inhalers are suitable, for instance, to treat asthma, allergies or other diseases and, in particular, they serve for the dosed administration of a drug that is delivered via the mouth or nose. In this context, one also speaks of so-called metered-dose aerosols. Especially when it comes to life-threatening diseases, it is important for the user to have information about how much of the substance is still left in the canister. As a rule, this is not visible since the pressurized canister that holds the sprayable substance is usually not made of a transparent material. This underscores the importance of an electronic unit to record the administered doses of the sprayable substance. This unit provides users with reliable information about the amount of sprayable substance that has been administered or that is still left in the canister, so that they can make sure that they always have an adequate supply of the sprayable substance they need.
Devices for the dosed administration of drugs are known in various configurations. For instance, European patent application EP 0 448 204 B1 discloses such a device having a one-piece housing with a receptacle for a canister that holds the sprayable substance. The housing has a hollow mouthpiece that is arranged at an angle relative to the longitudinal axis of the canister and through which the sprayable substance can be delivered and inhaled when a valve on the canister is actuated. The sprayable substance is administered in that the canister moves towards the housing and, in this process, the valve on the canister is actuated. In order to record the number of administered doses, the prior-art device is provided with an electronic unit that has a switch that is situated directly on the canister and that is actuated by it.
Another inhaler is described in European patent application EP 0 775 499 B1. Here, a unit that is supposed to show the number of administered doses is arranged on the upper end of the housing.
In the case of the inhaler described in U.S. Pat. No. 6,138,669, the number of administered doses is recorded by a sensor that measures the pressure pulse in the transfer channel of the mouthpiece.